1. Field of the Invention
This invention relates to a plasma etching electrode for dry etching devices for production of semiconductor devices, and a dry etching device including the same, more particularly to a highly heat-resistant plasma etching electrode for dry etching devices with 2 or more members composed of a silicon electrode plate supported by a pedestal being joined by an epoxy-based adhesive agent, and a dry etching device including the same.
2. Description of the Prior Art
As information devices represented by computers advance, the semiconductor integrated circuit as the main component of these devices is increasingly required to have higher degree of integration. In the production of a semiconductor device, the works are conducted in a clean working atmosphere, e.g., in a clean room, for meeting the performance requirements, because each production step as well as the stock material is extremely sensitive to contamination with impurities. It is needless to say that each component for the production facility is required not to produce impurities.
The wafer treatment processes, represented by ion implantation, dry etching and sputtering, are effected in a reaction chamber, frequently referred to as a chamber, which can be evacuated to a high degree of vacuum. The wafer treatment processes are increasingly required to meet the higher purity standards, as the degree of integration increases for semiconductor integrated circuits, with the result that the chamber and each of its components are required to have the material characteristics as free as possible of contamination with impurities.
Taking dry etching as an example, the component members inside of the chamber are described by referring to FIG. 3. The chamber normally includes a pair of electrodes, i.e., upper and lower electrodes, facing each other, the lower electrode being connected to an RF power source to produce a plasma between the counter electrodes. A silicon wafer is set immediately above the lower electrode via a mounting member, to be etched with an etchant gas in a plasma atmosphere.
Some of the conventional plasma etching electrodes, including an upper electrode, for dry etching devices have complicated shapes to be set in a chamber structure. The plasma etching electrode is often composed of the components of glassy carbon, silicon or silicon carbide (SiC), and assembling these components into a monolithic structure greatly increases the cost.
Therefore, the upper electrode for a dry etching device is composed of an electrode plate of silicon or the like which is joined to a pedestal (or support ring) of metal or metal oxide by brazing with a metal, e.g., indium or silver. These metallic brazing materials cause no problem with respect to electrical and thermal conductivity.
However, joining by brazing with a metal, e.g., indium, causes problems as wafer treating temperature increases to improve the plasma etching device performance. The brazing metal, although having a high adhesive strength, may be insufficient regarding its resistance to heat. For example, the faces joined by indium may be separated from each other, when exposed to a temperature exceeding 156xc2x0 C. as the melting point of indium. The joining needs pretreatment, e.g., undercoating treatment with a metallic film by sputtering, and other time-consuming works at high temperature, which tends to increase costs for workability and treatment.
Moreover, the brazing metal itself may cause contamination of the silicon wafer. Therefore, the joining method rarely has good etching characteristics for dry etching, and tends to lower the yield of the semiconductor device, or silicon wafer.
Several attempts have been made to solve these problems. For example, U.S. Pat. No. 5,074,456 proposes an upper electrode joined using a metal-filled epoxies, and U.S. Pat. No. 6,073,577 proposes an upper electrode joined using a metal particles-containing elastomeric materials.
These inventions claim that the electrode plate and pedestal can be joined to each other more precisely, because of uniformly decreased thickness of the adhesive layer to a size of the metal particles, keeping good parallelism between the upper and lower electrodes and avoiding contamination with impurities.
However, these inventions have lower thermal conductivity between the electrode plate and pedestal, in spite of the metallic filler present in the adhesive layer, than the case where they are joined by a brazing material, possibly causing a temperature distribution between the electrode plate periphery and center, and hence deteriorating the etching characteristics.
Therefore, the joined type plasma etching electrode is required to have electrical and thermal conductance and heat resistance at the joint, and a type of plasma etching electrode excellent in these characteristics has been strongly demanded.
It is an object of the present invention to provide a plasma etching electrode which does not become contaminated with impurities, has good thermal and electrical conductance and heat resistance at the joint between the electrode plate and pedestal (or supporting ring), and hence improves the etching characteristics and silicon wafer yield by solving the problems involved with conventional plasma etching electrodes for dry etching devices. It is another object to provide a dry etching device including the same.
The inventors of the present invention have found, after having extensively studied for developing the optimum plasma etching electrode for dry etching devices in order to solve the above problems, that the electrode plate and pedestal can be securely joined even at high temperatures and, at the same time, good thermal and electrical conductance can be realized between the electrode and pedestal when graphite, which does not become contaminated with impurities, is used as the material for the pedestal and joined to the electrode plate of silicon by a polycarbodiimide-containing epoxy resin-based adhesive agent incorporated with carbon as the thermal and electrical conductive filler, thereby achieving the present invention.
The first aspect of the invention provides a highly heat-resistant plasma etching electrode for dry etching devices, comprising an electrode plate of silicon supported by and securely and uniformly joined to a pedestal by an adhesive agent, wherein
(a) the pedestal is made of graphite, and
(b) an epoxy resin containing polycarbodiimide resin and carbon powder are used as the adhesive agent.
The second aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the first aspect, wherein the adhesive agent contains 5 to 20 parts by weight of a polycarbodiimide resin and 12 to 440 parts by weight of carbon powder per 100 parts by weight of an epoxy resin.
The third aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the first aspect, wherein the adhesive agent contains a curing agent or curing promoter.
The fourth aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the third aspect, wherein the curing agent is of a compound selected from the group consisting of an amine-, hydrazine-, phenol- and acid anhydride-based compound, and the curing promoter is of a compound selected from the group consisting of imidazole, a tertiary amine and metallic complex.
The fifth aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the third aspect, wherein the curing agent or curing promoter is incorporated at 1 to 150 parts by weight per 100 parts by weight of the epoxy resin.
The sixth aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the first aspect, wherein the polycarbodiimide resin is an aromatic-based compound.
The seventh aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the first aspect, wherein the epoxy resin is a bisphenol A type one.
The eighth aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the first aspect, wherein the carbon powder has a Young""s modulus of elasticity of 6xc3x97109 to 68xc3x97109N/m2.
The ninth aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the first aspect, wherein the pedestal is coated with glass-like carbon entirely except for the joint with the electrode plate of silicon.
The tenth aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the ninth aspect, wherein the coating film of glass-like carbon has a thickness of 1 to 3 xcexcm.
The eleventh aspect of the invention provides a plasma etching electrode for dry etching devices which is the same as that of the first aspect, wherein the electrode plate of silicon is made of single-crystalline silicon and has through-holes.
The twelfth aspect of the invention provides a dry etching device which includes the plasma etching electrode of one of the first to eleventh aspect.
As described above, the present invention relates to a highly heat-resistant plasma etching electrode for dry etching devices, comprising an electrode plate of silicon supported by and securely and uniformly joined to a pedestal by an adhesive agent, wherein (a) the pedestal is made of graphite, and (b) an epoxy resin containing polycarbodiimide resin and carbon powder are used for the adhesive agent. The preferred embodiments of the invention include the following:
(1) The plasma etching electrode for dry etching devices which is the same as that of the first aspect of the invention wherein the electrode serves as the upper electrode.